#1 relay turns the fans on low speed, then #2and #3 turn on also for high speed. All controlled by the PCM.
Cooling Fans
Thread Starter
Instructor
Joined: Feb 2009
Posts: 204
Likes: 0
From: Pinellas Park Florida
Cooling Fans
I noticed yesterday that both of my cooling fans come when I start the car. The motor is cold and the AC is on. I thought that the second fan didn't come on until the temperature reached around 238 deg. Is something wrong? It is a 94 LT1.
Melting Slicks
Joined: Jun 1999
Posts: 2,949
Likes: 23
From: Bowling Green KY
2 are controlled by the PCM - the other one links up to A/C - if A/C is on the relay will cause both fan's to come on, completely independently of PCM control.
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
Wrong. The PCM controls the fans. Period. I don't think a 94 has three relays.
Last edited by MK 82; Sep 29, 2009 at 12:31 AM.
Le Mans Master
Joined: Aug 1999
Posts: 7,339
Likes: 137
From: WilkesBarre PA
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
All of these Years are PCM driven based on input from the Pressure Sensor mounted on the High a/c line. The only way to see that signal is is with a Scanner. There's no gage on any vehicle that will give the pressure/temp of the stuff in the Condensor - but the PCM knows what it is based on this signal. In order for it blow cold air - or to keep it from blowing a hole in the hood - it's critical to keep the gas within a fairly narrow pressure/temperature range and that's what the PCM is doing when it drives the fans. That pressure/temp range is well below the thermostat which is one of the reasons it needs one. Coolant temperatures will be lower with the a/c on, because as you may be seeing, the fan(s) come on sooner - blow longer - and on some of the laters Years, at a much higher speed. Assuming it's blowing cold air, it's normal - if it's not, then you probably should figure out why, but in most cases it's because it's plugged up and no matter how much air flows across the condensor coils, it isn't doing what it should be doing.
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